vendredi 1 juillet 2016

A view of the LHCb experimental cavern. (Image: Claudia Marcelloni/CERN)

On 28 June, the LHCb collaboration reported the observation of three new "exotic" particles and the confirmation of the existence of a fourth one in data from the Large Hadron Collider (LHC). These particles seem to be formed by four quarks (the fundamental constituent of the matter inside all the atoms of the universe): two quarks and two antiquarks (that is, a tetraquark). Due to their non-standard quark content, the newly observed particles have been included in the broad category of so-called exotic particles, although their exact theoretical interpretation is still under study.

The quark model, proposed in 1964 by Murray Gell-Mann and George Zweig, is the most valid classification scheme of hadrons (all the composite particles) that has been found so far and it is part of the Standard Model of particle physics. In this model, hadrons are classified according to their quark content. However, it has been for a long-held mystery that all observed hadrons were formed either by a pair of quark-antiquark (mesons) or by three quarks (baryons) only. But, in the last decade several collaborations have found evidence of the existence of particles formed by more than three quarks. For example, in 2009 the CDF collaboration found one of these, called X(4140) – where the number in parentheses is its reconstructed mass in megaelectronvolts. This result was then confirmed later by a new CDF analysis, and by the CMS and D0 collaborations.

Nevertheless, until now, the X(4140) quantum numbers – characteristic numbers with which the properties of a specific particle are identified – were not fully determined, and this ambiguity exposed the theoretical explanation to uncertainty. The LHCb collaboration could determine the X(4140) quantum numbers with high precision. This result has a large impact on the possible theoretical interpretations, and indeed it excludes some of the previously proposed theories on its nature.

While the X(4140) had already been seen, the observation of the three new exotic particles with higher masses, called X(4274), X(4500) and X(4700), has been announced for the first time. Even though the four particles all contain the same quark composition, they each have a unique internal structure, mass and their own sets of quantum numbers.

Graphic above: The image shows the data (black dots) of the mass distribution resulting from the association of the J/ψ and φ mesons, where the contribution of the four exotic particles is put into evidence by the four peaking structures at the bottom. Graphic Credit: CERN.

These results are based on a detailed analysis of the decay of a B+ meson into mesons called J/ψ, φ and K+, where the new particles appear as intermediate ones decaying to a pair of J/ψ and φ mesons. To perform this research, the LHCb physicists used the full set of data collected during the first LHC run, from 2010 to 2012. The large signal yield efficiently collected with the LHCb detector has allowed LHCb scientists to discover those three new particles that were (literally, see the picture) peaking out from the data.

This news comes in addition to the discovery of the first two pentaquark particles by the LHCb collaboration last year.

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 21 Member States.

NASA's Juno mission, launched nearly five years ago, will soon reach its final destination: the most massive planet in our solar system, Jupiter. On the evening of July 4, at roughly 9 p.m. PDT (12 a.m. EDT, July 5), the spacecraft will complete a burn of its main engine, placing it in orbit around the king of planets.

During Juno's orbit-insertion phase, or JOI, the spacecraft will perform a series of steps in preparation for a main engine burn that will guide it into orbit. At 6:16 p.m. PDT (9:16 p.m. EDT), Juno will begin to turn slowly away from the sun and toward its orbit-insertion attitude. Then 72 minutes later, it will make a faster turn into the orbit-insertion attitude.

At 7:41 p.m. PDT (10:41 p.m. EDT), Juno switches to its low-gain
antenna. Fine-tune adjustments are then made to the spacecraft's
attitude. Twenty-two minutes before the main engine burn, at 7:56 p.m.
PDT (10:56 p.m. EDT), the spacecraft spins up from 2 to 5 revolutions
per minute (RPM) to help stabilize it for the orbit insertion burn.

At 8:18 p.m. PDT (11:18 p.m. EDT), Juno's 35-minute main-engine burn will begin. This will slow it enough to be captured by the giant planet’s gravity. The burn will impart a mean change in velocity of 1,212 mph (542 meters a second) on the spacecraft. It is performed in view of Earth, allowing its progress to be monitored by the mission teams at NASA's Jet Propulsion Laboratory in Pasadena, California, and Lockheed Martin Space Systems in Denver, via signal reception by Deep Space Network antennas in Goldstone, California, and Canberra, Australia.

After the main engine burn, Juno will be in orbit around Jupiter. The spacecraft will spin down from 5 to 2 RPM, turn back toward the sun, and ultimately transmit telemetry via its high-gain antenna.

Juno starts its tour of Jupiter in a 53.5-day orbit. The spacecraft saves fuel by executing a burn that places it in a capture orbit with a 53.5-day orbit instead of going directly for the 14-day orbit that will occur during the mission's primary science collection period. The 14-day science orbit phase will begin after the final burn of the mission for Juno’s main engine on October 19.

Jupiter Into the Unknown (NASA Juno Mission Trailer)

JPL manages the Juno mission for NASA. The mission's principal investigator is Scott Bolton of Southwest Research Institute in San Antonio. The mission is part of NASA's New Frontiers Program, managed at the agency's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems in Denver built the spacecraft.

Following its historic first-ever flyby of Pluto, NASA’s New Horizons mission has received the green light to fly onward to an object deeper in the Kuiper Belt, known as 2014 MU69. The spacecraft’s planned rendezvous with the ancient object – considered one of the early building blocks of the solar system -- is Jan. 1, 2019.

“The New Horizons mission to Pluto exceeded our expectations and even today the data from the spacecraft continue to surprise,” said NASA’s Director of Planetary Science Jim Green. “We’re excited to continue onward into the dark depths of the outer solar system to a science target that wasn’t even discovered when the spacecraft launched.”

Exploring the Solar System

Based upon the 2016 Planetary Mission Senior Review Panel report, NASA this week directed nine extended missions to plan for continued operations through fiscal years 2017 and 2018. Final decisions on mission extensions are contingent on the outcome of the annual budget process.

In addition to the extension of the New Horizons mission, NASA determined that the Dawn spacecraft should remain at the dwarf planet Ceres, rather than changing course to the main belt asteroid Adeona.

Green noted that NASA relies on the scientific assessment by the Senior Review Panel in making its decision on which extended mission option to approve. “The long-term monitoring of Ceres, particularly as it gets closer to perihelion – the part of its orbit with the shortest distance to the sun -- has the potential to provide more significant science discoveries than a flyby of Adeona,” he said.

Also receiving NASA approval for mission extensions, contingent on available resources, are: the Mars Reconnaissance Orbiter (MRO), Mars Atmosphere and Volatile EvolutioN (MAVEN), the Opportunity and Curiosity Mars rovers, the Mars Odyssey orbiter, the Lunar Reconnaissance Orbiter (LRO), and NASA’s support for the European Space Agency’s Mars Express mission.

This NASA/ESA Hubble Space Telescope image reveals the iridescent interior of one of the most active galaxies in our local neighborhood — NGC 1569, a small galaxy located about eleven million light-years away in the constellation of Camelopardalis (The Giraffe).

This galaxy is currently a hotbed of vigorous star formation. NGC 1569 is a starburst galaxy, meaning that — as the name suggests — it is bursting at the seams with stars, and is currently producing them at a rate far higher than that observed in most other galaxies. For almost 100 million years, NGC 1569 has pumped out stars more than 100 times faster than the Milky Way!

As a result, this glittering galaxy is home to super star clusters, three of which are visible in this image — one of the two bright clusters is actually the superposition of two massive clusters. Each containing more than a million stars, these brilliant blue clusters reside within a large cavity of gas carved out by multiple supernovae, the energetic remnants of massive stars.

In 2008, Hubble observed the galaxy's cluttered core and sparsely populated outer fringes. By pinpointing individual red giant stars, Hubble’s Advanced Camera for Surveys enabled astronomers to calculate a new — and much more precise — estimate for NGC 1569’s distance. This revealed that the galaxy is actually one and a half times farther away than previously thought, and a member of the IC 342 galaxy group.

Astronomers suspect that the IC 342 cosmic congregation is responsible for the star-forming frenzy observed in NGC 1569. Gravitational interactions between this galactic group are believed to be compressing the gas within NGC 1569. As it is compressed, the gas collapses, heats up and forms new stars.

Hubble and the sunrise over Earth

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

jeudi 30 juin 2016

NASA's Jupiter-bound Juno spacecraft has entered the planet's magnetosphere, where the movement of particles in space is controlled by what's going on inside Jupiter.

"We've just crossed the boundary into Jupiter's home turf," said Juno Principal Investigator Scott Bolton of Southwest Research Institute, San Antonio. "We're closing in fast on the planet itself and already gaining valuable data."

Data Recorded as Juno Crossed Jovian Bow Shock

Video above: This chart presents data the Waves investigation on NASA's Juno spacecraft recorded as the spacecraft crossed the bow shock just outside of Jupiter's magnetosphere on July 24, 2016. Audio accompanies the animation, with volume and pitch correlated to the amplitude and frequency of the recorded waves. Video Credits: NASA/JPL-Caltech/SwRI/Univ. of Iowa.

Juno is on course to swing into orbit around Jupiter on July 4. Science instruments on board detected changes in the particles and fields around the spacecraft as it passed from an environment dominated by the interplanetary solar wind into Jupiter's magnetosphere. Data from Juno's Waves investigation, presented as audio stream and color animation, indicate the spacecraft's crossing of the bow shock just outside the magnetosphere on June 24 and the transit into the lower density of the Jovian magnetosphere on July 25.

Infographic: Juno, Built to Withstand Intense Radiation Environments

Infographic above: Juno has been headed for Jupiter since 2011 to study the gas giant’s atmosphere, aurora, gravity and magnetic field. This infographic illustrates the radiation environments Juno has traveled through on its journey near Earth and in interplanetary space. Credits: NASA's Goddard Space Flight Center.

"The bow shock is analogous to a sonic boom," said William Kurth of the University of Iowa in Iowa City, lead co-investigator for the Waves investigation. "The solar wind blows past all the planets at a speed of about a million miles per hour, and where it hits an obstacle, there's all this turbulence."

The obstacle is Jupiter's magnetosphere, which is the largest structure in the solar system.

Data Recorded as Juno Entered Magnetosphere

Video above: This chart presents data that the Waves investigation on NASA's Juno spacecraft recorded as the spacecraft entered Jupiter's magnetosphere on July 25, 2016, while approaching Jupiter. Audio accompanies the animation, with volume and pitch correlated to the amplitude and frequency of the recorded waves. Video Credits: NASA/JPL-Caltech/SwRI/Univ. of Iowa.

"If Jupiter's magnetosphere glowed in visible light, it would be twice the size of the full moon as seen from Earth," Kurth said. And that's the shorter dimension of the teardrop-shaped structure; the dimension extending outward behind Jupiter has a length about five times the distance between Earth and the sun.

Out in the solar wind a few days ago, Juno was speeding through an environment that has about 16 particles per cubic inch (one per cubic centimeter). Once it crossed into the magnetosphere, the density was about a hundredfold less. The density is expected to climb again, inside the magnetosphere, as the spacecraft gets closer to Jupiter itself. The motions of these particles traveling under the control of Jupiter's magnetic field will be one type of evidence Juno examines for clues about Jupiter's deep interior.

Image above: NASA's Juno spacecraft obtained this color view on June 28, 2016, at a distance of 3.9 million miles (6.2 million kilometers) from Jupiter. Image Credits: NASA/JPL-Caltech/SwRI/MSSS.

While this transition from the solar wind into the magnetosphere was predicted to occur at some point in time, the structure of the boundary between those two regions proved to be unexpectedly complex, with different instruments reporting unusual signatures both before and after the nominal crossing.

"This unusual boundary structure will itself be the subject of scientific investigation," said Barry Mauk of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, who is the instrument lead for the Jupiter Energetic-Particle Detector Instrument (JEDI) on Juno.

Some of the wind-sculpted sand ripples on Mars are a type not seen on Earth, and their relationship to the thin Martian atmosphere today provides new clues about the atmosphere's history.

The determination that these mid-size ripples are a distinct type resulted from observations by NASA's Curiosity Mars rover. Six months ago, Curiosity made the first up-close study of active sand dunes anywhere other than Earth, at the "Bagnold Dunes" on the northwestern flank of Mars' Mount Sharp.

(Click on the image for enlarge)

Image above: Two sizes of ripples are evident in this Dec. 13, 2015, view of a top of a Martian sand dune, from NASA's Curiosity Mars rover. Sand dunes and the smaller type of ripples also exist on Earth. The larger ripples are a type not seen on Earth nor previously recognized as a distinct type on Mars. Image Credits: NASA/JPL-Caltech/MSSS.

"Earth and Mars both have big sand dunes and small sand ripples, but on Mars, there's something in between that we don't have on Earth," said Mathieu Lapotre, a graduate student at Caltech in Pasadena, California, and science team collaborator for the Curiosity mission. He is the lead author of a report about these mid-size ripples published in the July 1 issue of the journal Science.

Both planets have true dunes -- typically larger than a football field -- with downwind faces shaped by sand avalanches, making them steeper than the upwind faces.

Earth also has smaller ripples -- appearing in rows typically less than a foot (less than 30 centimeters) apart -- that are formed by wind-carried sand grains colliding with other sand grains along the ground. Some of these "impact ripples" corrugate the surfaces of sand dunes and beaches.

Images of Martian sand dunes taken from orbit have, for years, shown ripples about 10 feet (3 meters) apart on dunes' surfaces. Until Curiosity studied the Bagnold Dunes, the interpretation was that impact ripples on Mars could be several times larger than impact ripples on Earth. Features the scale of Earth's impact ripples would go unseen at the resolution of images taken from orbit imaging and would not be expected to be present if the meter-scale ripples were impact ripples.

"As Curiosity was approaching the Bagnold Dunes, we started seeing that the crest lines of the meter-scale ripples are sinuous," Lapotre said. "That is not like impact ripples, but it is just like sand ripples that form under moving water on Earth. And we saw that superimposed on the surfaces of these larger ripples were ripples the same size and shape as impact ripples on Earth."

Image above: This May 11, 2016, self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Okoruso" drilling site on lower Mount Sharp's "Naukluft Plateau." The scene is a mosaic of multiple images taken with the arm-mounted Mars Hands Lens Imager (MAHLI). Image Credits: NASA/JPL-Caltech/MSSS.

Besides the sinuous crests, another similarity between the mid-size ripples on Mars and underwater ripples on Earth is that, in each case, one face of each ripple is steeper than the face on the other side and has sand flows, as in a dune. Researchers conclude that the meter-scale ripples are built by Martian wind dragging sand particles the way flowing water drags sand particles on Earth -- a different mechanism than how either dunes or impact ripples form. Lapotre and co-authors call them "wind-drag ripples."

"The size of these ripples is related to the density of the fluid moving the grains, and that fluid is the Martian atmosphere," he said. "We think Mars had a thicker atmosphere in the past that might have formed smaller wind-drag ripples or even have prevented their formation altogether. Thus, the size of preserved wind-drag ripples, where found in Martian sandstones, may have recorded the thinning of the atmosphere."

The researchers checked ripple textures preserved in sandstone more than 3 billion years old at sites investigated by Curiosity and by NASA's Opportunity Mars rover. They found wind-drag ripples about the same size as modern ones on active dunes. That fits with other lines of evidence that Mars lost most of its original atmosphere early in the planet's history.

Other findings from Curiosity's work at the Bagnold Dunes point to similarities between how dunes behave on Mars and Earth.

"During our visit to the active Bagnold Dunes, you might almost forget you’re on Mars, given how similar the sand behaves in spite of the different gravity and atmosphere. But these mid-sized ripples are a reminder that those differences can surprise us," said Curiosity Project Scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory in Pasadena.

After examining the dune field, Curiosity resumed climbing the lower portion of Mount Sharp. The mission is investigating evidence about how and when ancient environmental conditions in the area evolved from freshwater settings favorable for microbial life, if Mars has ever hosted life, into conditions drier and less habitable. For more information about Curiosity, visit: http://mars.jpl.nasa.gov/msl

Astronomers are using the NASA/ESA Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the Solar System, Jupiter. This observation programme is supported by measurements made by NASA’s Juno spacecraft, currently on its way to Jupiter.

Auroras on Jupiter

Jupiter, the largest planet in the Solar System, is best known for its colourful storms, the most famous being the Great Red Spot. Now astronomers have focused on another beautiful feature of the planet, using the ultraviolet capabilities of the NASA/ESA Hubble Space Telescope.

The extraordinary vivid glows shown in the new observations are known as auroras [1]. They are created when high energy particles enter a planet’s atmosphere near its magnetic poles and collide with atoms of gas. As well as producing beautiful images, this programme aims to determine how various components of Jupiter’s auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the Sun.

Timelapse of Jupiter’s auroras

This observation programme is perfectly timed as NASA’s Juno spacecraft is currently in the solar wind near Jupiter and will enter the orbit of the planet in early July 2016. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself; a perfect collaboration between a telescope and a space probe [2].

“These auroras are very dramatic and among the most active I have ever seen”, says Jonathan Nichols from the University of Leicester, UK, and principal investigator of the study. “It almost seems as if Jupiter is throwing a firework party for the imminent arrival of Juno.”

To highlight changes in the auroras Hubble is observing Jupiter daily for around one month. Using this series of images it is possible for scientists to create videos that demonstrate the movement of the vivid auroras, which cover areas bigger than the Earth.

Timelapse of Jupiter’s auroras (2)

Not only are the auroras huge, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. Whilst on Earth the most intense auroras are caused by solar storms — when charged particles rain down on the upper atmosphere, excite gases, and cause them to glow red, green and purple — Jupiter has an additional source for its auroras.

The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanos.

The new observations and measurements made with Hubble and Juno will help to better understand how the Sun and other sources influence auroras. While the observations with Hubble are still ongoing and the analysis of the data will take several more months, the first images and videos are already available and show the auroras on Jupiter’s north pole in their full beauty.

Hubble orbiting Earth

Notes:

[1] Jupiter’s auroras were first discovered by the Voyager 1 spacecraft in 1979. A thin ring of light on Jupiter's nightside looked like a stretched-out version of our own auroras on Earth. Only later on was it discovered that the auroras were best visible in the ultraviolet.

[2] This is not the first time astronomers have used Hubble to observe the auroras on Jupiter, nor is it the first time that Hubble has cooperated with space probes to do so. In 2000 the NASA/ESA/ASI Cassini spacecraft made its closest approach to Jupiter and scientists used this opportunity to gather data and images about the auroras simultaneously from Cassini and Hubble (heic0009). In 2007 Hubble obtained images in support of its sister NASA Mission New Horizons which used Jupiter's gravity for a manoeuvre on its way to Pluto (opo0714a).More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Rosetta is set to complete its mission in a controlled descent to the surface of its comet on 30 September.

The mission is coming to an end as a result of the spacecraft’s ever-increasing distance from the Sun and Earth. It is heading out towards the orbit of Jupiter, resulting in significantly reduced solar power to operate the craft and its instruments, and a reduction in bandwidth available to downlink scientific data.

Rosetta approaching comet

Combined with an ageing spacecraft and payload that have endured the harsh environment of space for over 12 years – not least two years close to a dusty comet – this means that Rosetta is reaching the end of its natural life.

Unlike in 2011, when Rosetta was put into a 31-month hibernation for the most distant part of its journey, this time it is riding alongside the comet. Comet 67P/Churyumov-Gerasimenko’s maximum distance from the Sun (over 850 million km) is more than Rosetta has ever journeyed before. The result is that there is not enough power at its most distant point to guarantee that Rosetta’s heaters would be able to keep it warm enough to survive.

Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet.

Where will Rosetta be on 30 September?

The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including very-high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion.

Communications will cease, however, once the orbiter reaches the surface, and its operations will then end.

“We’re trying to squeeze as many observations in as possible before we run out of solar power,” says Matt Taylor, ESA Rosetta project scientist. “30 September will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science. That is what the Rosetta mission was launched for and we have years of work ahead of us, thoroughly analysing its data.”

Rosetta’s operators will begin changing the trajectory in August ahead of the grand finale such that a series of elliptical orbits will take it progressively nearer to the comet at its closest point.

Close-up view of the comet

“Planning this phase is in fact far more complex than it was for Philae’s landing,” says Sylvain Lodiot, ESA Rosetta spacecraft operations manager. “The last six weeks will be particularly challenging as we fly eccentric orbits around the comet – in many ways this will be even riskier than the final descent itself.

“The closer we get to the comet, the more influence its non-uniform gravity will have, requiring us to have more control on the trajectory, and therefore more manoeuvres – our planning cycles will have to be executed on much shorter timescales.”

A number of dedicated manoeuvres in the closing days of the mission will conclude with one final trajectory change at a distance of around 20 km about 12 hours before impact, to put the spacecraft on its final descent.

The region to be targeted for Rosetta’s impact is still under discussion, as spacecraft operators and scientists examine the various trade-offs involved, with several different trajectories being examined.

Broadly speaking, however, it is expected that impact will take place at about 50 cm/s, roughly half the landing speed of Philae in November 2014.

Commands uploaded in the days before will automatically ensure that the transmitter as well as all attitude and orbit control units and instruments are switched off upon impact, to fulfill spacecraft disposal requirements.

In any case, Rosetta’s high-gain antenna will very likely no longer be pointing towards Earth following impact, making any potential communications virtually impossible.

A challenging environment

In the meantime, science will continue as normal, although there are still many risks ahead. Last month, the spacecraft experienced a ‘safe mode’ while only 5 km from the comet as a result of dust confusing the navigation system. Rosetta recovered, but the mission team cannot rule out this happening again before the planned end of the mission.

“Although we’ll do the best job possible to keep Rosetta safe until then, we know from our experience of nearly two years at the comet that things may not go quite as we plan and, as always, we have to be prepared for the unexpected,” cautions Patrick Martin, ESA Rosetta’s mission manager.

“This is the ultimate challenge for our teams and for our spacecraft, and it will be a very fitting way to end the incredible and successful Rosetta mission.”

Notes for Editors:

Details regarding the end of mission scenario are subject to change. Further information will be announced once available.

Europe’s proposed Asteroid Impact Mission is set to become humanity’s first mission to a double asteroid, and ESA’s first to a small body since Rosetta put down its lander on Comet 67P/Churyumov–Gerasimenko. Here are 10 key facts:

1. AIM has a trio of goals: to demonstrate key technologies for future deep-space missions, to investigate asteroid deflection techniques for planetary defence, and to revolutionise scientific understanding of asteroids.

2. AIM will have a ringside seat for the collision of a separate NASA spacecraft called DART with the asteroid’s tiny moon, gathering invaluable data that would help save Earth from impacts in the future should a real deflection mission be needed. These two ESA & NASA missions are collectively called the Asteroid Impact & Deflection Assessment (AIDA) mission.

The AIM spacecraft

3. AIM is a mission in a hurry. It must be built and ready to fly for a firm October/–November 2020 launch window in order to reach the Didymos binary asteroid system by June 2022, coinciding with Didymos’s exceptionally close approach to Earth.

4. AIM will perform detailed surface and internal structure investigations of the smaller 163- m- diameter ‘Didymoon’ in orbit around the 775- m diameter main asteroid both before and after the DART impact, to assess changes in its condition as well as its orbit. The closest precedent to this collision would be the 2005 impact strike of NASA’s Deep Impact probe with Comet Tempel 1, but that comet was a mountain-sized 6 km across, whereas Didymoon is only the size of the Great Pyramid of Giza.

Mascot-2 lander model

5. AIM’s instruments currently under study include a high-resolution visible imager, infrared imager, and high- and low-frequency radars, the former to build up a 10- cm-resolution surface map, the latter to sound deep beneath the surface of the asteroid.

6. The mission is designed to carry a microlander called Mascot-2, based on its twin Mascot-1 currently flying on-board Japan’s Hayabusa-2. Powered by a solar array, Mascot-2 would image the surface in visible and infrared light, and beam radar signals through the asteroid for its AIM mothership to pick up on the other side. In case of a landing in a non-illuminated area, a ‘mobility mechanism’ would let the shoebox-sized microlander jump to another location.

AIM mission objectives

7. AIM will also carry Europe’s first deep-space CubeSats. Several concepts being investigated would all contribute and complement AIM’s objectives with additional close-up measurements. Final selection will be made in January 2017.

8. Intended to be launched on Soyuz or the maiden flight of the Ariane 6 rocket, AIM will measure just 1.4 x 1.4 x 1.9 m (with solar arrays stowed). With a maximum mass of 835 kg at launch and about the size of a large office desk, AIM is much more compact than the lorry-sized Rosetta.

AIM mission objectives

9. AIM will return science data to Earth from deep- space using an ambitious long-distance optical communications system, which would also double as an altimeter and ‘laser radar’ lidar mapper for scientific use, combined with a novel ‘holographic’ modulated metasurface antenna.

10. The mission, set to be presented for approval by European space ministers in December, will demonstrate various key technologies for follow-on deep space and resource utilisation missions, including inter-satellite links between AIM and its microlander and CubeSats, as well as advanced spacecraft navigation and guidance systems to allow semi-autonomous low-gravity landing and proximity operations around Didymoon.

mercredi 29 juin 2016

The long-lasting effects of El Niño are projected to cause an intense fire season in the Amazon, according to the 2016 seasonal fire forecast from scientists at NASA and the University of California, Irvine.

Image above: The smoke from multiple fires in the Mato Grosso region of Brazil rises over forested and deforested areas in this astronaut photograph taken from the International Space Station on Aug. 19, 2014. Image Credit: NASA.

El Niño conditions in 2015 and early 2016 altered rainfall patterns around the world. In the Amazon, El Niño reduced rainfall during the wet season, leaving the region drier at the start of the 2016 dry season than any year since 2002, according to NASA satellite data.

Wildfire risk for the dry season months of July to October this year now exceeds fire risk in 2005 and 2010, drought years when wildfires burned large areas of Amazon rainforest, said Doug Morton, an Earth scientist at NASA’s Goddard Space Flight Center who helped create the fire forecast.

"Severe drought conditions at the start of the dry season set the stage
for extreme fire risk in 2016 across the southern Amazon," Morton said.

Image above: On a scale of zero to 100, the risk of severe fire activity in July, August and September is high for six states in Braxil (Acre, Amazonas, Maranhao, Mato Grosso, Para and Rondonia), three departments in Bolivia (El Beni, Pando, and Santa Cruz), and one country (Peru). Image Credits: Yang Chen, University of California, Irvine.

The Amazon fire forecast uses the relationship between climate and active fire detections from NASA satellites to predict fire season severity during the region’s dry season. Developed in 2011 by scientists at University of California, Irvine and NASA’s Goddard Space Flight Center, the forecast model is focused particularly on the link between sea surface temperatures and fire activity. Warmer sea surface temperatures in the tropical Pacific (El Niño) and Atlantic oceans shift rainfall away from the Amazon region, increasing the risk of fires during dry season months.

The team also uses data on terrestrial water storage from the joint NASA/German Aerospace Center (DLR) Gravity Recovery and Climate Experiment (GRACE) mission to follow changes in groundwater during the dry season. GRACE measurements serve as a proxy for the dryness of soils and forests.

The NASA and UC-Irvine scientists have worked with South American official and scientists to make them aware of the forecast in recent years. Liana Anderson, a Brazilian scientist from the National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN), said that “fire forecasts three to six months before peak fire activity are important to identify areas with higher fire probability for integrated planning in support of local actions.”

For 2016, El Niño-driven conditions are far drier than 2005 and 2010 – the last years when the region experienced drought. The team has also developed a web tool to track the evolution of the Amazon fire season in near real time. Estimated fire emissions from each forecast region are updated daily, based on the relationship between active fire detections – made by the Moderate resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite – and fire emissions data from the Global Fire Emissions Database (GFED) in previous years. So far, however, the region has seen more fires to date than those years, another indicator that aligns with the fire severity forecast.

Graphics above: An analysis of data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows greater soil water deficits in 2016 than previous drought years with high Amazon fire activity. Graphics Credits: Yang Chen, University of California, Irvine.

"When trees have less moisture to draw upon at the beginning of the dry season, they become more vulnerable to fire, and evaporate less water into the atmosphere," said UC-Irvine scientist Jim Randerson, who collaborated with UC-Irvine scientist Yang Chen on building the forecast model. "This puts millions of trees under stress and lowers humidity across the region, allowing fires to grow bigger than they normally would."

Fires in the Amazon have local, regional, and long-distance impacts. Agricultural fires that escape their intended boundaries can damage neighboring croplands and Amazon forests. Even slow-moving forest fires cause severe forest degradation, as Amazon rainforest trees are not adapted to fire. Together, intentional fires for agricultural management, deforestation, and wildfires generate massive smoke plumes that degrade regional air quality, exacerbating problems with asthma and respiratory illness. Smoke from Amazon fires eventually flows south and east over major urban centers in southern Brazil, including São Paulo and Rio de Janeiro, contributing to air quality concerns.

While scientists have been working with South American officials to broadcast the results of the fire forecasts and increase awareness of fire risk, they also said that the work could lead to better wildfire forecasts in other regions of the world. The team recently identified 9 regions outside the Amazon where fire season risk can also be forecast 3-6 months ahead of peak fire activity. It may be possible to build operational seasonal fire forecasts for much of Central America and for many countries in Southeast Asia, Randerson said.

NASA's Juno spacecraft will make its long anticipated arrival at Jupiter on July 4. Coming face-to-face with the gas giant, Juno will begin to unravel some of the greatest mysteries surrounding our solar system's largest planet, including the origin of its massive magnetosphere.

Magnetospheres are the result of a collision between a planet's intrinsic magnetic field and the supersonic solar wind. Jupiter's magnetosphere – the volume carved out in the solar wind where the planet’s magnetic field dominates –extends up to nearly 2 million miles (3 million kilometers). If it were visible in the night sky, Jupiter's magnetosphere would appear to be about the same size as Earth’s full moon. By studying Jupiter's magnetosphere, scientists will gain a better understanding about how Jupiter's magnetic field is generated. They also hope to determine whether the planet has a solid core, which will tell us how Jupiter formed during the earliest days of our solar system.

Exploring Jupiter's Magnetic Field

Video above: NASA is sending the Juno spacecraft to Jupiter, to peer beneath its cloudy surface and explore the giant planet's structure and magnetic field. Juno's twin magnetometers, built at Goddard Space Flight Center, will give scientists their first look within Jupiter at the powerful dynamo that drives its magnetic field.

In order to look inside the planet, the science team equipped Juno with a pair of magnetometers. The magnetometers, which were designed and built by an in-house team of scientists and engineers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, will allow scientists to map Jupiter's magnetic field with high accuracy and observe variations in the field over time.

"The best way to think of a magnetometer is like a compass," said Jack Connerney, deputy principal investigator and head of the magnetometer team at Goddard. "Compasses record the direction of a magnetic field. But magnetometers expand on that capability and record both the direction and magnitude of the magnetic field."

The magnetometer sensors rest on a boom attached to one of the solar arrays, placing them about 40 feet (12 meters) from the body of the spacecraft. This helps ensure that the rest of the spacecraft does not interfere with the magnetometer.

However, the sensor orientation changes in time with the mechanical distortion of the solar array and boom resulting from the extremely cold temperatures of deep space. This distortion would limit the accuracy of the magnetometer measurements if not measured.

To ensure that the magnetometers retain their high accuracy, the team paired the instruments with a set of four cameras. These cameras measure the distortion of the magnetometer sensors in reference to the stars to determine their orientation.

"This is our first opportunity to do very precise, high-accuracy mapping of the magnetic field of another planet," Connerney said. "We are going to be able to explore the entire three-dimensional space around Jupiter, wrapping Jupiter in a dense net of magnetic field observations completely covering the sphere."

One of the mysteries the team hopes to answer is how Jupiter's magnetic field is generated. Scientists expect to find similarities between Jupiter's magnetic field and that of Earth.

Magnetic fields are produced by what are known as dynamos — convective motion of electrically conducting fluid inside planets. As a planet rotates, the electrically susceptible liquid swirls around and drives electric currents, inducing a magnetic field. Earth's magnetic field is generated by liquid iron in the planet's core.

"But with Jupiter, we don't know what material is producing the planet's magnetic field,” said Jared Espley, Juno program scientist for NASA Headquarters, Washington. “What material is present and how deep down it lies is one of the questions Juno is designed to answer."

The observations made by Juno's magnetometers will also add to our understanding of Earth's dynamo, the source of our planet’s magnetic field, which lies deep beneath a magnetized layer of rocks and iron.

Imagine Earth's crust strewn with refrigerator magnets as you try to peer beneath the surface to observe the dynamo. The magnetization of Earth's crust will skew your measurements of the magnetic field.

"One of the reasons that the Juno mission is so exciting is because we can map Jupiter’s magnetic field without having to look through the crustal magnetic fields, which behave like a jumble of refrigerator magnets," Connerney said. "Jupiter has a gaseous envelope about it made of hydrogen and helium that gives us a clear and unobstructed view of the dynamo."

These observations will also add to the general understanding of how dynamos generate magnetic fields, including here on Earth.

"Any time we understand anything about another planet, we can take that knowledge and apply it to our knowledge about our own planet," Espley said. "We'll be looking at Juno's observations in a big-picture perspective."

NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft.

The brightest area on Ceres, located in the mysterious Occator Crater, has the highest concentration of carbonate minerals ever seen outside Earth, according to a new study from scientists on NASA's Dawn mission. The study, published online in the journal Nature, is one of two new papers about the makeup of Ceres.

Image above: The center of Ceres' mysterious Occator Crater is the brightest area on the dwarf planet. The inset perspective view shows new data on this feature: Red signifies a high abundance of carbonates, while gray indicates a low carbonate abundance. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASI/INAF.

"This is the first time we see this kind of material elsewhere in the solar system in such a large amount," said Maria Cristina De Sanctis, lead author and principal investigator of Dawn's visible and infrared mapping spectrometer. De Sanctis is based at the National Institute of Astrophysics, Rome.

At about 80 million years old, Occator is considered a young crater. It is 57 miles (92 kilometers) wide, with a central pit about 6 miles (10 kilometers) wide. A dome structure at the center, covered in highly reflective material, has radial and concentric fractures on and around it.

De Sanctis' study finds that the dominant mineral of this bright area is sodium carbonate, a kind of salt found on Earth in hydrothermal environments. This material appears to have come from inside Ceres, because an impacting asteroid could not have delivered it. The upwelling of this material suggests that temperatures inside Ceres are warmer than previously believed. Impact of an asteroid on Ceres may have helped bring this material up from below, but researchers think an internal process played a role as well.

More intriguingly, the results suggest that liquid water may have existed beneath the surface of Ceres in recent geological time. The salts could be remnants of an ocean, or localized bodies of water, that reached the surface and then froze millions of years ago.

"The minerals we have found at the Occator central bright area require alteration by water," De Sanctis said. "Carbonates support the idea that Ceres had interior hydrothermal activity, which pushed these materials to the surface within Occator."

The spacecraft's visible and infrared mapping spectrometer examines how
various wavelengths of sunlight are reflected by the surface of Ceres.
This allows scientists to identify minerals that are likely producing
those signals. The new results come from the infrared mapping component,
which examines Ceres in wavelengths of light too long for the eye to
see.

Last year, in a Nature study, De Sanctis' team reported that the surface of Ceres contains ammoniated phyllosilicates, or clays containing ammonia. Because ammonia is abundant in the outer solar system, this finding introduced the idea that Ceres may have formed near the orbit of Neptune and migrated inward. Alternatively, Ceres may have formed closer to its current position between Mars and Jupiter, but with material accumulated from the outer solar system.

The new results also find ammonia-bearing salts -- ammonium chloride and/or ammonium bicarbonate -- in Occator Crater. The carbonate finding further reinforces Ceres' connection with icy worlds in the outer solar system. Ammonia, in addition to sodium carbonate and sodium bicarbonate found at Occator, has been detected in the plumes of Enceladus, an icy moon of Saturn known for its geysers erupting from fissures in its surface. Such materials make Ceres interesting for the study of astrobiology.

"We will need to research whether Ceres' many other bright areas also contain these carbonates," De Sanctis said.

A separate Nature study in 2015 by scientists with the Dawn framing camera team hypothesized that the bright areas contain a different kind of salt: magnesium sulfate. But the new findings suggest sodium carbonate is the more likely constituent.

"It’s amazing how much we have been able to learn about Ceres' interior from Dawn's observations of chemical and geophysical properties. We expect more such discoveries as we mine this treasure trove of data," said Carol Raymond, deputy principal investigator for the Dawn mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Dawn science team members have also published a new study about the makeup of the outer layer of Ceres in Nature Geoscience, based on images from Dawn's framing camera. This study, led by Michael Bland of the U.S. Geological Survey, Flagstaff, Arizona, finds that most of Ceres' largest craters are more than 1 mile (2 kilometers) deep relative to surrounding terrain, meaning they have not deformed much over billions of years. These significant depths suggest that Ceres' subsurface is no more than 40 percent ice by volume, and the rest may be a mixture of rock and low-density materials such as salts or chemical compounds called clathrates. The appearance of a few shallow craters suggests that there could be variations in ice and rock content in the subsurface.

Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit:

Remember the stunning image Rosetta snapped of its own shadow last year? This was just one of twelve images taken by the OSIRIS narrow-angle camera during the 6 km flyby of Comet 67P/Churyumov-Gerasimenko on 14 February 2015 that captured the shadow, and which have today been released into the Archive Image Browser and the Planetary Science Archive.

Animation above showing Rosetta’s shadow move across the surface of Comet 67P/Churyumov-Gerasimenko during the 14 February 2015 flyby. The sequence lasts from 12:38 to 12:41 UT. The full resolution images can be downloaded from the Archive. Animation Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

This latest OSIRIS data release comprises 1357 narrow-angle camera images and 2162 wide-angle camera images from the period 20 December 2014 – 10 March 2015. During this time Rosetta was initially in ~28 km orbits around the comet. In early February the spacecraft moved out to 142 km before swooping past the comet at 6 km on 14 February and away again (this video visualizes Rosetta’s trajectory at that time).

The 14 February flyby was not only special because it was the closest Rosetta had ever been to the surface of the comet at that time but it also passed through a unique observational geometry: for a short time the Sun, spacecraft, and comet were exactly aligned. In this geometry, surface structures cast almost no shadows, and therefore the reflection properties of the surface material can be determined. As a side effect, Rosetta’s shadow could also be seen, cast on the surface of the comet as a fuzzy rectangular-shaped dark spot surrounded by a bright halo-like region. The shadow is fuzzy and somewhat larger than Rosetta itself, measuring approximately 20 x 50 metres. (For more information about this effect see last year’s blog post “Comet flyby: OSIRIS catches glimpse of Rosetta’s shadow"):http://orbiterchspacenews.blogspot.ch/2015/03/comet-flyby-osiris-catches-glimpse-of.html

Images above: Example of images from the OSIRIS wide-angle camera albums in the latest data release. Images Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

The data release also contains many other beauty shots of the comet from both near and far, with the wide-angle camera shots in particular capturing the comet’s ever-increasing activity at that time.

Also today, 540 new NAVCAM images were added to the Archive Image Browser. The latest batch cover the period 4-31 May 2016 and as such include images from the close flyby that took Rosetta to within 5 km of the surface.

mardi 28 juin 2016

This new image from the NASA/ESA Hubble Space Telescope shows a cosmic tadpole, with its bright head and elongated tail, wriggling through the inky black pool of space. Tadpole galaxies are rare and difficult to find in the local Universe. This striking example, named LEDA 36252, was explored as part of a Hubble study into their mysterious properties — with interesting results.

The Universe is a swirling pool of galaxies moving through the emptiness of space. Whilst spiral galaxies and ellipticals are the two main galaxy types in the Universe, there are also other, odder types — as shown in this image from the NASA/ESA Hubble Space Telescope, taken with the Wide Field Camera 3 (WFC3).

The galaxy LEDA 36252 — also known as Kiso 5639 — is an example of what is known as a tadpole galaxy because of their bright, compact heads and elongated tails [1]. Tadpole galaxies are unusual, and rare in the local Universe — in a sample of 10 000 galaxies within the local Universe, only 20 would be tadpoles — but they are more common in the early Universe.

Ground-based view of LEDA 36252

This image of LEDA 36252 was obtained as part of a scientific study into the galaxy’s properties [2]. It is an ideal cosmic laboratory for astronomers to study the accretion of cosmic gas, starburst activity, and the formation of globular star clusters.

The stars in tadpole galaxies are generally very old — living fossils from the early Universe and from the time when these galaxies formed. LEDA 36252 is in general no exception to that.

However, studying LEDA 36252 has led also to some unexpected results: its head contains a mass of surprisingly young stars with a total mass equivalent to some 10 000 Suns. These stars are grouped into large clusters and appear to consist mainly of hydrogen and helium with hardly any other elements. Astronomers think that this new burst of star formation was triggered when the galaxy accreted primordial gas — gas which was only very slightly enriched by other elements created by stellar fusion processes in the past — from its surroundings.

Zoom on LEDA 36252

Also the elongated tail, seen stretching away from the head and scattered with bright blue stars, contains at least four distinct star-forming regions. These appear to be older than the one in the head.

The observations also showed signs of strong stellar winds and supernova explosions, which have blasted holes through LEDA 36252’s head and created multiple cavities. Wispy filaments, comprising gas and some stars, extend away from the main body of the cosmic tadpole.

The WFC3 observations comprising this image cover a wide portion of the spectrum, including ultraviolet, optical, H-alpha, and infrared emission. Together, they paint a beautifully detailed picture of LEDA 36252.

Notes:

[1] There is a specific galaxy named the Tadpole Galaxy, which has been imaged by Hubble in the past. This galaxy was named for its stretched-out appearance, but it is a spiral, not a tadpole, galaxy.

[2] The study, entitled Hubble Space Telescope Observations of Accretion-Induced Star Formation in the Tadpole Galaxy Kiso 5639 by D. Elmegreen et al., is published in The Astrophysical Journal.

More information:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.